Romney faces mounting pressure to release tax returns now

IRMO, S.C. — Mitt Romney came under increasing pressure Wednesday to release his income tax returns immediately, rather than waiting until April, in an effort to contain the damage caused by his stumbling responses over two days.

Unanswered questions about his wealth threw the Republican presidential front-runner's campaign off balance and threatened to undercut his message in the final days before Saturday's potentially decisive primary in South Carolina, where a new poll showed his lead shrinking to 10 percentage points.

Meanwhile, ABC News will air an interview with Newt Gingrich's second wife, Marianne — with whom he has said he has no relationship — tonight on Nightline.

Romney launched a fresh assault Wednesday on Gingrich, calling the former House speaker's tenure in Washington "leadership by chaos" and likening him to former Vice President Al Gore.

"It's the private sector that creates jobs," the former Massachusetts governor said at a Spartanburg rally. "Congressmen taking credit for helping create jobs is like Al Gore taking credit for the Internet."

But the offensive did little to quiet a growing debate among Republicans about his tax returns.

Gingrich plans to release his returns today, teeing up the tax issue for a debate tonight in Charleston. Former Pennsylvania Sen. Rick Santorum said he would release his returns, too.

The issue has dogged Romney, a multimillionaire, since he first indicated he might not release his returns. After he shifted positions during a debate Monday and acknowledged Tuesday he has paid an effective tax rate of about 15 percent, GOP strategists said the political cost of delaying the release of his returns has escalated dramatically.

Obama starting ads: President Barack Obama is launching his first television ad of his re-election campaign, defending his energy record and citing his work to toughen ethics rules.

A campaign official said the ads will begin running today in at least six states that will be critical to his re-election bid — Iowa, Michigan, North Carolina, Ohio, Virginia and Wisconsin.